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Deep FoundationsDeep Foundations

Lesson 9Lesson 9 -- Topic 2Topic 2

Construction Monitoring andConstruction Monitoring andQuality AssuranceQuality Assurance

(Section 9.9)(Section 9.9)

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Learning OutcomesLearning Outcomes

At the end of this session, the At the end of this session, the

participant will be able to:participant will be able to:-- Recall pile driving equipmentRecall pile driving equipment-- Review wave equation analysisReview wave equation analysis

-- Assess pile Assess pile driveabilitydriveability

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Both the pile and the driving equipmentBoth the pile and the driving equipmentmust be sized to permit pile installationmust be sized to permit pile installation

to the designed geotechnical soilto the designed geotechnical soilresistance without damageresistance without damage

Pile Driving Equipment andPile Driving Equipment and

OperationOperation

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Figure 9-37

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Figure 9-38

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Driving System AnalysisDriving System Analysis

Fundamental pile driving mechanismFundamental pile driving mechanism

EN approachEN approach Wave equation approachWave equation approach

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The FundamentalThe Fundamental

Pile Driving FormulaPile Driving Formula

s

hW R

sRhW

ResistanceSoilof WorkEnergyHammer

RR

WW

SS

hh

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The EN Bearing GraphThe EN Bearing Graph

R =R =

2W h2W h

s+0.1s+0.1

Safe Load “ R”Safe Load “ R”

1/8”1/8”

Set “ s”Set “ s”

WW

hh

1/16”1/16” 1/24”1/24” 1/32”1/32”

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RR

100 200 300 400100 200 300 400

Blows per FootBlows per Foot

Find Blow CountFind Blow Count

For Given LoadFor Given Load

Limit ofLimit of DriveabilityDriveability

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Construction ConsiderationsConstruction Considerations

in Designin Design

Intelligent preparation of plan andIntelligent preparation of plan and

specifications can only be done by onespecifications can only be done by one

who understands the constructionwho understands the construction

operation as well as structural designoperation as well as structural designconceptsconcepts

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EN Formula Factor of SafetyEN Formula Factor of Safety

To find F.S. between P and R, revise ENRto be dimensionally correct and compare

the resulting equation for P with R

s

WHR =

( ) s6WH

12/11.0s

WH2

P =

+=

P6R =

W

H

sR

2 W H(ft)s(in) + 0.1

#

=P

Safety Factor = 6Safety Factor = 6

To find F.S. between P and R, revise ENRto be dimensionally correct and compare

the resulting equation for P with R

s

WHR =

( ) s6WH

12/11.0s

WH2

P =

+=

P6R =

W

H

sR

W

H

sR

2 W H(ft)s(in) + 0.1

#

=P

Safety Factor = 6Safety Factor = 6

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Dynamic Analysis of Pile DrivingDynamic Analysis of Pile Driving

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ImportantImportant

DrivingDrivingSystemSystem

PropertiesProperties

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Hammer Hammer

Impact hammers and vibratory hammersImpact hammers and vibratory hammers-- Numerous manufacturersNumerous manufacturers-- Variations in power source, configurations andVariations in power source, configurations and

rated energyrated energy

Mechanical efficiency determines percentageMechanical efficiency determines percentage

rated energy transmitted to the pilerated energy transmitted to the pile-- Typical values are 50% for air Typical values are 50% for air --steam, 70% forsteam, 70% for

diesel and 90% for hydraulicdiesel and 90% for hydraulic

Force wave shape characteristics areForce wave shape characteristics are

different for different hammer typesdifferent for different hammer types

-- Affects pile stress and pile penetration Affects pile stress and pile penetration

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Pile and AppurtenancesPile and Appurtenances

(Cushions, Helmets, etc.)(Cushions, Helmets, etc.) Stiffness of appurtenances (e.g., hammerStiffness of appurtenances (e.g., hammer

cushion) = AE/tcushion) = AE/t-- Major effect on blow count and stress transfer toMajor effect on blow count and stress transfer tothe pilethe pile

-- Must not degrade during driving resulting inMust not degrade during driving resulting indecreasing blow count and increasing pile stressdecreasing blow count and increasing pile stress

CrossCross--sectional area of pile is major factor insectional area of pile is major factor in

driveabilitydriveability-- The hammer energy is absorbed in strain ratherThe hammer energy is absorbed in strain ratherthan performing work (i.e., penetrating pile) forthan performing work (i.e., penetrating pile) for

long piles with smalllong piles with small c/sc/s areaarea

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SoilSoil

SetupSetup

RelaxationRelaxation

Important soil propertiesImportant soil properties-- QuakeQuake-- DampingDamping

Total soil resistance to be overcomeTotal soil resistance to be overcomeduring driving to estimated lengthduring driving to estimated length

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Wave Equation MethodologyWave Equation Methodology

A l i P d

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1. Soil model and ultimate capacityassumed.

2. Analysis set in motion by

selecting hammer efficiency.

3. Impact velocity of hammer mass

elements calculated from efficiency.

4. For each time step, the

acceleration, velocity, force, and

displacement for each element and

the pile toe are calculated based onforce equilibrium (F = ma).

5. Process continues until pile toe

rebounds.

6. Final set calculated for capacity.

Analysis Procedure Analysis Procedure

W E ti A li ti

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Develop driving criterionDevelop driving criterion

Blow count for a required ultimate capacityBlow count for a required ultimate capacity

blow count for capacity as a function of energy/strokeblow count for capacity as a function of energy/stroke

CheckCheck driveabilitydriveability

Blow count vs. Penetration depthBlow count vs. Penetration depth

Driving stressesDriving stresses vsvs penetration depthpenetration depth

Determine optimal driving equipmentDetermine optimal driving equipment

Driving timeDriving time

Refined matching analysisRefined matching analysis

Adjust input parameters to fit dynamic measurements Adjust input parameters to fit dynamic measurements

Wave Equation ApplicationsWave Equation Applications

IMPORTANT NOTESIMPORTANT NOTES

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IMPORTANT NOTESIMPORTANT NOTES

The wave equation analysis CANNOTThe wave equation analysis CANNOT

determine pile lengthdetermine pile length Does the method determine capacity?Does the method determine capacity?

I t t W E ti A l iI t t W E ti A l i

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Hammer Hammer -- ModelModel

-- Stroke and Stroke ControlStroke and Stroke Control-- Any Modifications Any Modifications

Driving SystemDriving System

-- Helmet Weight (including Striker Plate & Cushions)Helmet Weight (including Striker Plate & Cushions)

-- Hammer Cushion Material (E, A, t,Hammer Cushion Material (E, A, t, eer r ))-- Pile Cushion Material (E, A, t,Pile Cushion Material (E, A, t, eer r ))

Input to Wave Equation AnalysisInput to Wave Equation Analysis


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PilePile-- Length,Length,

-- Cross Sectional AreaCross Sectional Area-- Taper or Other NonTaper or Other Non--uniformitiesuniformities

-- Specific WeightSpecific Weight

-- Splice DetailsSplice Details-- Design LoadDesign Load

-- Ultimate CapacityUltimate Capacity

-- Pile Toe ProtectionPile Toe Protection



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SoilSoil-- Boring Locations with ElevationsBoring Locations with Elevations

-- Soil DescriptionsSoil Descriptions

-- NN--values or Other Strength Parametersvalues or Other Strength Parameters vsvs DepthDepth

-- Elevation of ExcavationElevation of Excavation-- Elevation of Pile CutElevation of Pile Cut --off off

-- Elevation of Water TableElevation of Water Table

-- Scour Depth or Other Later ExcavationsScour Depth or Other Later Excavations

Contract No.: Structure Name and/or No.:Project:

Pile Dr iving Co ntractor or Subcontractor:

County:

Contract No.: Structure Name and/or No.:Project:

Pile Dr iving Co ntractor or Subcontractor:

County:

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PilePile

DrivingDrivingandand

EquipmentEquipmentData FormData Form

County:(Piles driven by)

Manufacturer: Model No.:Hammer Type: Serial No.:

Manufacturers Max imum Rated Energy: (ft-lbs)Hammer Stroke at Maximum Rated Energy: (ft)

Range in Op erating Energy: to (ft-lbs)

Range in Op erating Stroke: to (ft)Ram Weight: (kips)

Modifications:

Striker Weight: (kips) Diameter: (in)Plate Thickness: (in)

Material #1 Material #2(for Composite Cu shion)

Name: Name:Hammer Area: (in2) Area: ( in2)

Cushion Thickness/Plate: (in) Thickness/Plate: (in)

No. of Plates: No. of Plates:

Total Thickness of Ha mm er Cushion:

Helmet

(Drive Head) Weight: (kips)

Pile Material:

Cushion Area: (in2) T hick nes s /S h ee t: (i n)

No. of Sheets:

Total Thickness of Pile Cushion: (in)

Pile Type:Wal l T hic kn ess : ( in ) T ap er :

Cross Sectional Area: (in2) Weight/Ft:Pile

Ordered Length: (ft)

Design Load: (kips)Ultim ate Pile Capacity: (kips)

Description of Splice:

Driv ing Shoe/Closure Plate De scription:

Submitted By: Date:

Telephone No.: Fax No.:Telephone No.: Fax No.:

County:(Piles driven by)

Manufacturer: Model No.:Hammer Type: Serial No.:

Manufacturers Max imum Rated Energy: (ft-lbs)Hammer Stroke at Maximum Rated Energy: (ft)

Range in Op erating Energy: to (ft-lbs)

Range in Op erating Stroke: to (ft)Ram Weight: (kips)

Modifications:

Striker Weight: (kips) Diameter: (in)Plate Thickness: (in)

Material #1 Material #2(for Composite Cu shion)

Name: Name:Hammer Area: (in2) Area: ( in2)

Cushion Thickness/Plate: (in) Thickness/Plate: (in)

No. of Plates: No. of Plates:

Total Thickness of Ha mm er Cushion:

Helmet

(Drive Head) Weight: (kips)

Pile Material:

Cushion Area: (in2) T hick nes s /S h ee t: (i n)

No. of Sheets:

Total Thickness of Pile Cushion: (in)

Pile Type:Wal l T hic kn ess : ( in ) T ap er :

Cross Sectional Area: (in2) Weight/Ft:Pile

Ordered Length: (ft)

Design Load: (kips)Ultim ate Pile Capacity: (kips)

Description of Splice:

Driv ing Shoe/Closure Plate De scription:

Submitted By: Date:

Telephone No.: Fax No.:Telephone No.: Fax No.:

R

a

m

Anvil

Output from Wave EquationOutput from Wave Equation

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Output from Wave EquationOutput from Wave Equation

Analysis Analysis For a given hammer, driving system,For a given hammer, driving system,

pile and soil model combination, thepile and soil model combination, theWEA output includes the following:WEA output includes the following:-- Predicted blow countPredicted blow count

-- Pile stressesPile stresses-- Delivered hammer energyDelivered hammer energy

Example Output from WaveExample Output from Wave

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Example Output from WaveExample Output from Wave

Equation AnalysisEquation Analysis Output is usually plotted for interpretationOutput is usually plotted for interpretation

WAVE EQUATION SUMMARY

Rul t Kips

BlowCountBPF

StrokeFt.

TensileStress

Ksi

CompressiveStress Ksi

TransferEnergyFt-Kip

35.0 7 3.27 -0.73 1.68 13.680.0 16 3.27 -0.32 1.71 13.6

140.0 30 3.27 -0.20 1.73 13.0160.0 35 3.27 -0.14 1.73 13.0195.0 49 3.27 -0.00 1.75 12.8225.0 63 3.27 0.0 1.96 12.7

280.0 119 3.27 0.0 2.34 12.6350.0 841 3.27 0.0 2.75 12.5

Interpretation of WEA OutputInterpretation of WEA Output

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Interpretation of WEA OutputInterpretation of WEA Output

Output is usuallyOutput is usuallyplotted forplotted for

interpretationinterpretation

Following plots areFollowing plots areusually createdusually created-- Blow countBlow count vsvs

resistanceresistance-- Blow countBlow count vsvs

stressstress

Bearing GraphBearing Graph

Constant stroke forConstant stroke for

air air --steam hammer steam hammer

Diesel Hammer at ConstantDiesel Hammer at Constant

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Diesel Hammer at ConstantDiesel Hammer at Constant

StrokeStroke

0

Ru , Kips

300

200

100

5 10 15 20

d e f

8.0

6.5

5.0

Ru =180

Kips

Stroke (ft)

0

Ru , Kips

300

200

100

5 10 15 20

d e f

8.0

6.5

5.0

Ru =180

Kips

Stroke (ft)

Variable StrokeVariable Stroke – – Diesel HammerDiesel Hammer

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0

Stroke ft

BPI (b)

5 10 15 20

d’

e

’

f’

Ru = 180 Kips

3

4

5

6

7

8

9

0

Stroke ft

BPI (b)

5 10 15 20

d’

e

’

f’

Ru = 180 Kips

3

4

5

6

7

8

9

Variable Stroke Diesel Hammer

Driving StressesDriving Stresses

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Driving StressesDriving Stresses

In almost all cases, the highest stressIn almost all cases, the highest stress

levels in a pile occur during pile drivinglevels in a pile occur during pile driving High driving stresses are necessary toHigh driving stresses are necessary to

achieve pile penetrationachieve pile penetration

WEA can predict driving stressesWEA can predict driving stresses

Compare predicted stresses to safeCompare predicted stresses to safe

stress levelsstress levels

Table 9Table 9--1010

General Criteria for PileGeneral Criteria for Pile

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General Criteria for PileGeneral Criteria for Pile

DriveabilityDriveability Acceptable driving stresses Acceptable driving stresses

-- Table 9Table 9--1010 Hammer blows between 30 to 144Hammer blows between 30 to 144 bpf bpf

for friction piles and higher blows offor friction piles and higher blows of

short duration for end bearing pilesshort duration for end bearing piles

Example 9Example 9-44

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Example 9Example 9--44

Example: Determine If The 14” SquareConcrete Pile Can Be Driven To A DrivingCapacity Of 225 Kips By Using The WaveEquation Output Summary. Assume The

Concrete Compressive Strength Is 4000 psi And The Pile Prestress Force Is 700 psi.

WAVE EQUATION OUTPUT SUMMARY

Rult Kips

BlowCountBPF

StrokeFt.

TensileStress

Ksi

CompressiveStress Ksi

35.0 7 3.27 -0.73 1.68

80.0 16 3.27 -0.32 1.71140.0 30 3.27 -0.20 1.73160.0 35 3.27 -0.14 1.73

195.0 49 3.27 -0.00 1.75225.0 63 3.27 0.0 1.96

280.0 119 3.27 0.0 2.34350.0 841 3.27 0.0 2.75

SolutionSolution

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SolutionSolution

Acceptable Acceptable driveabilitydriveability depends ondepends on

achieving the hammer blows betweenachieving the hammer blows between30 and 14430 and 144 bpf bpf as the driving resistanceas the driving resistance

and allowable compressive and tensileand allowable compressive and tensile

stresses are not exceededstresses are not exceeded

At At RRultult = 225 kips, blow count = 63= 225 kips, blow count = 63 bpf bpf

-- Between 30 and 144Between 30 and 144 bpf bpf -- OkayOkay

SolutionSolution

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SolutionSolution

Based on Table 9Based on Table 9--1010

Allowable compressive stress Allowable compressive stress

Maximum compressive stress fromMaximum compressive stress fromWEA = 1.96WEA = 1.96 ksiksi = 1,960= 1,960 psipsi < 2,700< 2,700 psipsi-- OkayOkay

0.85 f'c - f e = 3400 – 700 = 2700 psi

SolutionSolution

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SolutionSolution

Based on Table 9Based on Table 9--1010

Allowable tensile stress Allowable tensile stress

Maximum tensile stress from WEA =Maximum tensile stress from WEA =0.7300.730 ksiksi = 730= 730 psipsi < 890< 890 psipsi-- OkayOkay

Analyzed driving system is approved Analyzed driving system is approved

3 (f'c ) +f pe = 190 + 760 = 890 psi

W ngth 4 0

’

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120

100806040

20

0

20

40

60

80

100

120

R e s

i s t a

n c

e - T

o n

s

Blow Per Foot

Wave

Equation P i l e L

e n g t h

P i l e L e n

g t h 8 0 ’

P i l e L

e n g t h 1

2 0 ’

Engineering News

Formula All Lengths

Student Exercise 8Student Exercise 8

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The soil profile shows the calculated drivingThe soil profi le shows the calculated drivingresistance in each soil layer at each footingresistance in each soil layer at each footing

for the proposed 12” diameter steel pipefor the proposed 12” diameter steel pipepiles (piles (fyfy=36=36 ksiksi). Using maximum driving). Using maximum drivingresistance at any footing, find the anticipatedresistance at any footing, find the anticipatedmaxiumummaxiumum driving stress and blow countdriving stress and blow countfrom wave equation summaries shown for 3from wave equation summaries shown for 3pile sizes. Compare these values to thepile sizes. Compare these values to therecommended friction piles values for blowrecommended friction piles values for blow

count and driving stress to determinecount and driving stress to determineminimum acceptable pile wall thickness forminimum acceptable pile wall thickness forthe pipe piles at this sitethe pipe piles at this site


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Soil ProfileSoil Profile

*10T

*50T

*10T*10T

*10T*10T*30T

*120T*120T*120T*120T*120T

Student Exercise 8Student Exercise 8 -- SummariesSummaries

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Student Exercise 8 SummariesGRLWEAP S & F STUDENT EXERCISE 0.250

WALL THICKNESS

Rult Kips Bl Ct bpf Stroke (eq.

Ft)

Min str. ksi Max str.

ksi

Enthru kip-

ft

260.0 35.3 3.25 -0.85 36.34 14.8

360.0 111.8 3.25 -0.98 42.07 13.8

GRLWEAP S & F STUDENT EXERCISE 0.312

WALL THICKNESS


Ft)


ksi

Enthru kip-

ft

260.0 31.8 3.25 -0.68 28.58 15.1

360.0 72.9 3.25 -0.70 35.98 14.2

GRLWEAP S & F STUDENT EXERCISE 0.375

WALL THICKNESS


Ft)


ksi

Enthru kip-

ft

260.0 30.2 3.25 -0.45 24.67 15.2360.0 58.8 3.25 -0.95 30.47 14.5

Student Exercise 8Student Exercise 8 -- SolutionSolution

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Student Exercise 8Student Exercise 8 SolutionSolution

Select Pile 3, 0.375″ Wall Thickness,

Which meets both the Blow Count andStress Criteria.

Pile 1: 0.250″ wall thickness (9.77 in2)

Maximum Stress 42

Blow Count 112

Pile 2: 0.312″ wall thickness (12.19 in

2

)

Maximum Stress 36

Blow Count 73

Pile 3: 0.375″ wall thickness (14.60 in2)

Maximum Stress 30.4

Blow Count 59

OK N.G.

StudentStudent

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StudentStude t

Exercise 9Exercise 9--HammerHammer

Approval Approval Pile DesignPile Design

capacity = 115kcapacity = 115k Pile DrivingPile Driving

resistance = 300kresistance = 300k

Should youShould you

accept theaccept the

hammer?hammer?


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WEA OutputWEA Output


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Plots of WEA OutputPlots of WEA Output


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Solution SummarySolution SummaryAcceptable Driving Stresses:Maximum Compressive Stress = (0.85 × 5,000 psi) – 700 psi = 3,550 psi

Maximum Tensile Stress = (3 × √5,000 psi) + 700 psi =912 psi

Acceptable Blow Count Range: 30-144 blows/foot

Wave Equation Results: 300 Kips Driving Resistance

Max (compressive) stress = 1.9 ksi = 1,900 psi < 3,550

psi okayMin (tensile) stress = -0.28 ksi = -280 psi

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g

At the end of this session, the At the end of this session, the

participant will be able to:participant will be able to:-- Recall pile driving equipmentRecall pile driving equipment-- Review wave equation analysisReview wave equation analysis

-- Assess pile Assess pile driveabilitydriveability

Any Questions? Any Questions?

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yy

THE RO AD TO

UNDERS T ANDING

SOILS

AND

FOUND A TIONS

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